Few studies to date have considered the extent to which children's weight gain and loss during a dietary treatment may be influenced by parents' psychological factors. This study proposes to evaluate the relationship between parents' psychological characteristics, their eating behaviour and the degree of obesity among their children, before and after 1 yr of treatment. Forty-nine couples with children suffering from obesity were studied. Our data suggest that the mothers' characteristics are more important than those of the fathers' in cases of both children's obesity and weight-loss. The study found that mothers with a more serious psychiatric symptomatology and a more disturbed personality were associated with more severe obesity in children. Children who lost less weight were younger and had an obese mother with a neurotic tendency.